ebc- if you live close to a BIG town-like over 20k- look for a good local shop - they can be much more helpful than this forum- [tho its nice to compare notes]- i dont know 'bout 10 spd but i have used ultegra 9 spd for both -

If you have the old 9 speed Ultegras, the front shifter was designed to handle both double and triple. A few years back, when I started riding seriously again, I rode Ultegra 9 speed for a year on a triple, found I didn't need all those rings, so swapped for a double.

The front changer did both as advertised, but was much better as a double shifter than it ever was on triple rings. I fitted a new double Ultegra crankset with double BB, a short cage fr der. and short cage rear der. and off she went.

10 speed - Shimano now make double and triple specific front shifters. You'd have to check with a higher power to see if the triple could be fudged into working a double.

I believe Dereck is right about the Ultegra shifters being designed to accept both triple and double rings. I had Ultegra on an older steel frame with a 126mm rear triangle width and even though I was using the a double ring instead of the triple I found the extra click helped for trim adjust on the FD when in the big ring little cog combo.

I can confirm bikenut71's experience - I converted a triple 105 to a double compact and used the extra "throw" for trimming. Works fine. In fact, I rode that bike yesterday: it's my winter gravel road bike.

I have a mechanic friend who said that it sometimes helps to splurge on a front derailer if you go the compact crank route. If you just can't get it to shift smoothly and noise-free throughout the range, try a compact derailer.